Morse Numbers vs. Letters

gen.php

<?php
// run as: php gen.php > morse.dat
// then run gnuplot morse.gnuplot

$f = new NumberFormatter("en", NumberFormatter::SPELLOUT);

for ($i = 0; $i < 5000000; $i++){
    $letters = strlen(morse($f->format($i)));
    $numbers = strlen((string) $i) * 5;

    echo "{$i} {$numbers} {$letters}\n";
}

function morse($in){
    $lookup = [
        "a" => ".-",
        "b" => "-...",
        "c" => "-.-.",
        "d" => "-..",
        "e" => ".",
        "f" => "..-.",
        "g" => "--.",
        "h" => "....",
        "i" => "..",
        "j" => ".---",
        "k" => "-.-",
        "l" => ".-..",
        "m" => "--",
        "n" => "-.",
        "o" => "---",
        "p" => ".--.",
        "q" => "--.-",
        "r" => ".-.",
        "s" => "...",
        "t" => "-",
        "u" => "..-",
        "v" => "...-",
        "w" => ".--",
        "x" => "-..-",
        "y" => "-.--",
        "z" => "--.."
    ];

    $out = "";
    foreach(str_split($in) as $letter){
        $out .= $lookup[$letter]?? "";
    }

    return $out;
}

morse.gnuplot

set datafile separator " "

set terminal pngcairo size 1200,800
set output "morse.png"

set title "Morse Numbers vs. Letters"
set xlabel "Number"
set ylabel "Chars"

set grid

set style data line
set key off

plot 'morse.dat' using 1:2, 'morse.dat' using 1:3